Ack/nack transmission for multi-carrier operation

ABSTRACT

Techniques for acknowledging data transmissions in a multi-carrier wireless communication network are disclosed. In some aspects, a user equipment (UE) receives a data transmission on at least one component carrier (CC) in a plurality of configured CCs. The UE determines acknowledgement/negative acknowledgement (ACK/NACK) information for the data transmission and determines an uplink channel for sending the ACK/NACK information. When the ACK/NACK information is sent on a PUCCH, the UE may perform power control based on which CCs in the plurality of configured CCs data is received. When the ACK/NACK information is sent on a PUSCH, the UE may determine a number of resource elements based on its CC configuration.

The present application is a divisional of co-pending, commonlyassigned, U.S. patent application Ser. No. 13/209,388 entitled “ACK/NACKTRANSMISSION FOR MULTI-CARRIER OPERATION,” filed on Aug. 13, 2011, whichitself claims priority to provisional U.S. Application No. 61/374,210,entitled “METHODS AND APPARATUS FOR ACK/NACK RELATED DESIGN FOR CARRIERAGGREGATION IN LTE-A NETWORKS,” filed Aug. 16, 2010, and incorporatedherein by reference in its entirety.

BACKGROUND

I. Field

The present disclosure relates generally to communication and, morespecifically, to techniques for supporting communication in amulti-carrier wireless communication network.

II. Background

Wireless communication networks are widely deployed to provide variouscommunication content such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA)networks.

A wireless communication network may include a number of base stationsthat can support communication for a number of user equipments (UEs). AUE may communicate with a base station via the downlink and uplink. Thedownlink (or forward link) refers to the communication link from thebase station to the UE, and the uplink (or reverse link) refers to thecommunication link from the UE to the base station.

Some wireless communication networks support operation on multiplecomponent carriers (CCs). A CC may refer to a range of frequencies usedfor communication and may be associated with certain characteristics.For example, a CC may be associated with system information describingoperation on the CC. A CC may also be referred to as a carrier, a cell,a serving cell, a frequency channel, etc.

SUMMARY

Techniques for sending acknowledgement/negative acknowledgement(ACK/NACK) information in a multi-carrier wireless communication networkare disclosed. A user equipment (UE) may be configured for operation ona plurality of component carriers (CCs). The UE may receive one or moredownlink grants on one or more physical downlink control channels(PDCCHs) on one or more of its configured CCs. The UE may also receive adata transmission on one or more physical downlink shared channels(PDSCHs) on one or more of its downlink CCs and may determine ACK/NACKinformation for the received data transmission. The UE may select anuplink channel for the sending the ACK/NACK information and maydetermine a manner of sending the ACK/NACK information on the selecteduplink channel as described in the present disclosure.

In one aspect, the UE receives a data transmission on a plurality ofconfigured CCs and determines ACK/NACK information for the datatransmission. The UE determines an uplink channel for sending theACK/NACK information which may be a physical uplink control channel(PUCCH) or a physical uplink shared channel (PUSCH). When the PUCCH isutilized, the UE may perform power control for sending the ACK/NACKinformation on the PUCCH based on the CCs on which the data transmissionis received (i.e., CCs on which the PDSCH is detected). Alternatively,when the PUSCH is utilized, the UE may determine a number of resourceelements for sending the ACK/NACK information on the PUSCH based on itsconfigured CCs. The multi-carrier UE may thus utilize a different set ofCCs (detected CCs or configured CCs) for sending ACK/NACK information onits uplink channels.

In one aspect, the UE receives a data transmission on a plurality of CCsand determines ACK/NACK information for acknowledging the datatransmission on the PUCCH. This may include determining a total numberof transport blocks which are received in the data transmission over theplurality of CCs. The total number of transports blocks may bedetermined based on a transmission mode and/or DCI format of each CC onwhich data transmission is detected. The UE may determine a transmitpower for sending the ACK/NACK information based on the total number oftransport blocks, and may send the ACK/NACK information to a basestation on the PUCCH in accordance with the determined transmit power.

In another aspect, the UE may receive a data transmission on at leastone CC in a plurality of configured CCs and may determine ACK/NACKinformation for acknowledging the data transmission on the PUSCH. The UEmay determine a number of resource elements for sending the ACK/NACKinformation based on the plurality of configured CCs. This may includedetermining a number of ACK/NACK bits for the configured CCsirrespective of the number of CCs on which the data transmission isdetected in a downlink subframe. In one particular example, the UE maysum the number of ACK/NACK bits associated with a transmission mode ofeach configured CC to determine total ACK/NACK bits upon which thenumber of resource elements is based. The UE may send the ACK/NACKinformation on the PUSCH based on the determined number of resourceelements.

Various additional aspects of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication network.

FIG. 2 shows an exemplary frame structure for frequency divisionduplexing.

FIG. 3 shows an exemplary frame structure for time division duplexing.

FIGS. 4A and 4B show examples of carrier aggregation.

FIG. 5 shows aspects of data transmission on multiple CCs with HARQ.

FIG. 6 shows an example of determining an ACK/NACK bitwidth in amulti-carrier wireless communication network.

FIG. 7 shows an example of a downlink assignment index (DAI) for amulti-carrier wireless communication network.

FIG. 8 shows a process for sending ACK/NACK information.

FIG. 9 shows a process for receiving ACK/NACK information.

FIG. 10 shows a process for sending ACK/NACK information on a PUCCH.

FIG. 11 shows a process for receiving ACK/NACK information on a PUCCH.

FIG. 12 shows a process for sending ACK/NACK information on a PUSCH.

FIG. 13 shows a process for receiving ACK/NACK information on a PUSCH.

FIG. 14 shows an exemplary base station and an exemplary UE such as canperform the exemplary processes described herein.

FIG. 15 shows additional aspects of a base station and a UE according tothe present disclosure.

DETAILED DESCRIPTION

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother wireless networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA), Time Division Synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), Ultra MobileBroadband (UMB), IEEE 802.11 (Wi-Fi and Wi-Fi Direct), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A), in both frequency divisionduplexing (FDD) and time division duplexing (TDD), are new releases ofUMTS that use E-UTRA, which employs OFDMA on the downlink and SC-FDMA onthe uplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, certain aspects of the techniquesare described below for LTE, and LTE terminology is used in much of thedescription below.

FIG. 1 shows a wireless communication network 100, which may be an LTEnetwork or some other wireless network. Wireless network 100 may includea number of evolved Node Bs (eNBs) 110 and other network entities. AneNB may be an entity that communicates with the UEs and may also bereferred to as a Node B, a base station, an access point, etc. Each eNBmay provide communication coverage for a particular geographic area andmay support communication for the UEs located within the coverage area.To improve network capacity, the overall coverage area of an eNB may bepartitioned into multiple (e.g., three) smaller areas. Each smaller areamay be served by a respective eNB subsystem. In 3GPP, the term “cell”can refer to a coverage area of an eNB and/or an eNB subsystem servingthis coverage area. In general, an eNB may support one or multiple(e.g., three) cells. The term “cell” may also refer to a carrier onwhich an eNB operates.

A network controller 130 may couple to a set of eNBs and providecoordination and control for these eNBs. Network controller 130 maycommunicate with the eNBs via a backhaul. The eNBs may also communicatewith one another, e.g., directly or indirectly via wireless or wirelinebackhaul.

UEs 120 may be dispersed throughout the wireless network, and each UEmay be stationary or mobile. A UE may also be referred to as a mobilestation, a terminal, an access terminal, a subscriber unit, a station,etc. A UE may be a cellular phone, a smart phone, a tablet, a wirelesscommunication device, a personal digital assistant (PDA), a wirelessmodem, a handheld device, a laptop computer, a cordless phone, awireless local loop (WLL) station, a netbook, a smartbook, etc. Forclarity, some of the description below refers to UE 120 x and eNB 110 x,which may be one of the UEs and one of the eNBs in wireless network 100.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition a frequency spectrum into multiple(N_(FFT)) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (N_(FFT))may be dependent on the system bandwidth. For example, the subcarrierspacing may be 15 kilohertz (KHz), and N_(FFT) may be equal to 128, 256,512, 1024 or 2048 for system bandwidth of 1.4, 3, 5, 10 or 20 megahertz(MHz), respectively.

Wireless network 100 may utilize FDD or TDD. For FDD, the downlink anduplink may be allocated separate frequency spectrum. Downlinktransmissions may be sent on one frequency spectrum, and uplinktransmissions may be sent on another frequency spectrum. For TDD, thedownlink and uplink may share the same frequency spectrum, and downlinkand uplink transmissions may be sent on the same frequency spectrum indifferent time intervals.

FIG. 2 shows an exemplary frame structure 200 for FDD in LTE. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each slot may include L symbol periods, e.g.,seven symbol periods for a normal cyclic prefix (as shown in FIG. 2) orsix symbol periods for an extended cyclic prefix. The 2L symbol periodsin each subframe may be assigned indices of 0 through 2L-1.

The available time frequency resources for each of the downlink anduplink may be partitioned into resource blocks. Each resource block maycover 12 subcarriers in one slot and may include a number of resourceelements. Each resource element may cover one subcarrier in one symbolperiod and may be used to send one modulation symbol, which may be areal or complex value.

FIG. 3 shows an exemplary frame structure 300 for TDD in LTE. Subframes0 and 5 are used for the downlink, subframe 2 is used for the uplink,and subframes 3, 4, 7, 8 and 9 may each be used for the downlink oruplink. Subframe 1 includes a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). Subframe 6 mayinclude only the DwPTS, or all three special fields, or a downlinksubframe. LTE supports a number of uplink-downlink configurations forTDD. Each uplink-downlink configuration indicates whether each subframeis a downlink subframe, an uplink subframe, or a special subframe. Theremay be as many as nine downlink subframes to one uplink subframe in aradio frame.

As shown in FIGS. 2 and 3, a subframe for the downlink (i.e., a downlinksubframe) may include a control region and a data region, which may betime division multiplexed (TDM). The control region may include thefirst Q symbol periods of the subframe, where Q may be equal to 1, 2, 3or 4. Q may change from subframe to subframe and may be conveyed in thefirst symbol period of the subframe. The data region may include theremaining 2L-Q symbol periods of the subframe and may carry data and/orother information for UEs.

An eNB may send downlink control information (DCI) on a physicaldownlink control channel (PDCCH) in the control region to a UE. The DCImay include a downlink grant, an uplink grant, power controlinformation, etc. The eNB may send data and/or other information on aphysical downlink shared channel (PDSCH) in the data region to the UE.

As shown in FIGS. 2 and 3, a subframe for the uplink (i.e., an uplinksubframe) may include a control region and a data region, which may befrequency division multiplexed (FDM). The control region may includeresource blocks near the two edges of the uplink spectrum (as shown inFIGS. 2 and 3) and may have a configurable size. The data region mayinclude all resource blocks not included in the control region.

A UE may send uplink control information (UCI) to an eNB on a physicaluplink control channel (PUCCH) in the control region of an uplinksubframe. The UCI may include ACKINACK information for a datatransmission received on the downlink, channel state information (CSI),scheduling request (SR), etc. The UE may send data or data and UCI tothe eNB on a physical uplink shared channel (PUSCH) in the data regionof the uplink subframe. The UE may transmit only the PUCCH or only thePUSCH (and not both) in a subframe in order to maintain a single-carrierwaveform, which may have a lower peak-to-average power ratio (PAPR). Anuplink transmission may span both slots of a subframe and may hop acrossfrequency.

Wireless network 100 may support operation on multiple CCs on thedownlink and one or more CCs on the uplink. Operation on multiple CCsmay be referred to as carrier aggregation. A CC for the downlink may bereferred to as a downlink CC, and a CC for the uplink may be referred toas an uplink CC. An eNB may transmit data and DCI on one or moredownlink CCs to a UE. As used herein, a data transmission may includeone or more transport blocks (which may also be referred to as PDSCHtransmissions) on one or more CC that are configured for the UE. Forexample, in a given subframe, the UE may receive multiple PDSCHtransmissions on multiple configured CCs. The UE may transmit data andUCI to the eNB on one or more uplink CCs.

FIG. 4A shows an example of continuous carrier aggregation. In thisexample, M CCs are shown as adjacent to each other in frequency, where Mmay be any integer value. Each CC may have a bandwidth of 20 MHz or lessand may be separately configured for a UE.

FIG. 4B shows an example of non-continuous carrier aggregation. In thisexample, M CCs are shown as separated from each other in frequency. Eachnon-contiguous CC may have a bandwidth of 20 MHz or less and may beseparately configured for a UE.

With carrier aggregation, data and control information may be sent andreceived on each CC. This may be achieved, for example, by using (i) aseparate inverse fast Fourier transform (IFFT) and a separatetransmitter for each CC at a transmitting entity and (ii) a separatefast Fourier transform (FFT) and a separate receiver for each CC at areceiving entity. A transmission comprising up to M concurrent OFDMsymbols or SC-FDMA symbols may be on up to M CCs in one symbol period.In another example, data and control information may be collectivelysent and received on all CCs. This may be achieved by using (i) a singleIFFT and a single transmitter for all M CCs at a transmitting entity and(ii) a single FFT and a single receiver for all M CCs at a receivingentity. A single OFDM symbol or SC-FDMA symbol may be transmitted on upto M CCs in one symbol period.

Wireless network 100 may support data transmission with hybrid automaticretransmission (HARQ) to improve reliability. For HARQ, a transmitter(e.g., an eNB) may send an initial transmission of a transport block andmay send one or more additional transmissions of the transport block, ifneeded, until the transport block is decoded correctly by a receiver(e.g., a UE), or the maximum number of transmissions of the transportblock has occurred, or some other termination condition is encountered.After each transmission of the transport block, the receiver may send anacknowledgement (ACK) if the transport block is decoded correctly, anegative acknowledgement (NACK) if the transport block is decoded inerror, or a discontinuous transmission (DTX) if the transport block ismissed. The transmitter may send another transmission of the transportblock if a NACK or a DTX is received and may terminate transmission ofthe transport block if an ACK is received. A transport block may also bereferred to as a packet, a codeword, a data block, etc.

FIG. 5 shows a scheme of transmitting DCI and data with HARQ on multiple(M) downlink CCs and transmitting UCI and data on one uplink CC. In thisexample, UE 120 x may periodically estimate the channel quality ofdifferent downlink CCs for eNB 110 x and may determine CSI for eachdownlink CC. The CSI may include channel quality indicator (CQI),precoding matrix indicator (PMI), rank indicator (RI), or a combinationthereof. RI may indicate the number of layers or spatial channels to usefor transmission of data. PMI may indicate a precoding matrix or vectorto use for precoding data prior to transmission. CQI may indicate achannel quality for each transport block. UE 120 x may periodically sendCSI for each downlink CC to eNB 110 x and/or may send CSI reports whentriggered by eNB 110 x.

eNB 110 x may receive CSI for all downlink CCs configured for UE 120 xand may use the CSI to select UE 120 x for transmission of data, toschedule UE 120 x on one or more downlink CCs and/or the uplink CC, andto select one or more modulation and coding schemes (MCSs) for eachdownlink CC on which UE 120 x is scheduled. eNB 110 x may process (e.g.,encode and modulate) one or more transport blocks for each scheduled CCbased on the one or more MCSs selected for that CC. eNB 110 x may thensend a transmission of one or more transport blocks (or a PDSCHtransmission) on each scheduled CC to UE 120 x.

UE 120 x may receive and decode the transmission of one or moretransport blocks on each scheduled CC in the plurality of configuredCCs. For each configured CC, UE 120 x may determine whether atransmission of one or more transport blocks is detected and, when atransmission is detected, whether each transport block is decodedcorrectly or in error. UE 120 x may generate an ACK for each transportblock decoded correctly and a NACK for each transport block decoded inerror. UE 120 x may send ACK/NACK information comprising ACKs and/orNACKs for all transport blocks received on all M downlink CCs in aparticular subframe. eNB 110 x may receive the ACK/NACK information fromUE 120 x, terminate transmission of each transport block for which anACK is received, and send another transmission of each transport blockfor which a NACK is received. UE 120 x may also transmit data to eNB 110x with the ACK/NACK information when there is data to send and when ithas been scheduled for transmission of data on the uplink CC.

As shown in FIG. 5, eNB 110 x may send a downlink grant to UE 120 x fora PDSCH transmission on a downlink CC. The downlink grant may includevarious parameters for receiving and decoding the PDSCH transmission onthe downlink CC. The downlink grant may be sent on the downlink CC onwhich the PDSCH transmission is sent or on another downlink CC. eNB 110x may also send an uplink (UL) grant for a data transmission on theuplink CC by UE 120 x. The uplink grant may include various parametersfor generating and sending the data transmission on a shared channel(e.g., PUSCH) of the uplink CC. The uplink grant may also include a CQIrequest. In this case, UE 120 x may send CSI with data on the PUSCH.

UE 120 x may transmit data and/or UCI, or neither, in a given subframe.The UCI may comprise only CSI, or only ACK/NACK, or both CSI andACK/NACK. UE 120 x may be configured to periodically send CSI for eachdownlink CC of interest, which may be referred to as periodic CQIreporting. In this case, the UE may periodically send CSI reports indesignated subframes determined by a schedule for periodic CSIreporting. Each CSI report may comprise CQI, PMI and/or RI for one ormore downlink CCs. UE 120 x may also be requested to send CSI for one ormore downlink CCs in any subframe, which may be referred to as aperiodicCSI reporting. This may be achieved by including a CSI request for oneor more downlink CCs in an uplink grant.

eNB 110 x may send DCI (e.g., a downlink grant and/or an uplink grant)to UE 120 x on the PDCCH on a downlink CC. When UE 120 x is scheduledfor a data transmission, eNB 110 x may send data on the PDSCH on adownlink CC. In a particular subframe, UE 120 x may send UCI (e.g., CSIand/or ACK/NACK) on the PUCCH on an uplink CC to eNB 110 x.Alternatively, when an uplink grant is received, UE 120 x may send onlydata or both data and UCI on the PUSCH on an uplink CC.

In general, UE 120 x may be configured with any number of downlink CCsand any number of uplink CCs for multi-carrier operation. For purposesof illustration in the description below, UE 120 x may be configuredwith up to five downlink CCs and up to five uplink CCs for multi-carrieroperation. In some examples, one downlink CC may be designated as adownlink primary CC (PCC), one uplink CC may be designated as an uplinkPCC, and each remaining CC may be referred to as a secondary CC (SCC).eNB 110 x may send certain information (e.g., grants, ACK/NACK, etc.) onthe downlink PCC to UE 120 x. UE 120 x may send certain information(e.g., CSI, ACK/NACK, scheduling request, etc.) on the uplink PCC to eNB110 x.

Table 1 lists different types of CC referred to in the descriptionherein.

TABLE 1 CC Type CC Type Description Configured CC A downlink CC that isconfigured for UE 120x. Activated CC A downlink CC that is configuredand activated/ enabled for use. Scheduled CC A downlink CC on which UE120x is scheduled for data transmission. Detected CC A downlink CC onwhich UE 120x receives a data transmission.

UE 120 x may be semi-statically configured with M downlink CCs and oneor more uplink CCs, e.g., via higher layer such as Radio ResourceControl (RRC). In general, M may be any value greater than one. In oneexemplary system, M may be less than or equal to five. Some or all ofthe configured CCs may be activated. An activated CC is a CC that a UEactively monitors on the downlink and/or actively transmits on theuplink. UE 120 x may not monitor a deactivated CC on the downlink, eventhough the CC is one of the configured CCs, which would result in powersavings. UE 120 x may be scheduled for data transmission on all or asubset of the configured CCs in a given subframe. For dynamicscheduling, a downlink grant may be sent for a transmission of one ormore transport blocks on each scheduled CC.

UE 120 x may detect a downlink grant on the PDCCH for a PDSCHtransmission on a downlink CC (a “detected CC”). UE 120 x may receivethe PDSCH transmission on the detected CC in accordance with thedownlink grant. The downlink grant may be sent on the same downlink CCon which the associated PDSCH transmission is sent. In this case, thedetected CC would be the downlink CC on which the downlink grant isreceived. The downlink grant may also be sent on one downlink CC, andthe associated PDSCH transmission may be sent on a different downlinkCC. For example, the downlink grant may include a carrier indicationfield (CIF) indicating the downlink CC on which the associated PDSCHtransmission is sent. In that case, UE 120 x may identify the detectedCC based on the CIF in the downlink grant. UE 120 x may detect some orall of the scheduled CCs, e.g., depending on whether UE 120 x missed anydownlink grants sent to UE 120 x. UE 120 x may receive PDSCHtransmissions on all detected CCs.

UE 120 x may be configured with M downlink CCs, and each downlink CC maybe associated with a particular transmission mode in a set of supportedtransmission modes. Table 2 lists the transmission modes supported inLTE Release 9. Transmission modes 1, 2, 5, 6 and 7 support single-inputsingle-output (SISO) or single-input multiple-output (SIMO)transmissions. Transmission modes 3, 4 and 8 support multiple-inputmultiple-output (MIMO) transmission.

TABLE 2 Transmission Modes Number of Transmission Transport Mode BlocksDescription 1 1 Transmission from a single eNB antenna port 2 1 Transmitdiversity 3 2 Open-loop spatial multiplexing 4 2 Closed-loop spatialmultiplexing 5 1 Multi-user MIMO 6 1 Closed-loop rank 1 precoding 7 1Transmission using UE-specific reference signal 8 2 Dual layertransmission

A transmission mode may be independently configured for each downlinkCC. The M downlink CCs for UE 120 x may be configured with the same ordifferent transmission modes.

One or more transport blocks may be sent on a downlink CC depending onthe transmission mode configured for the downlink CC. In particular, onetransport block may be sent on a downlink CC that is configured withtransmission mode 1, 2, 5, 6 or 7, and two transport blocks may be senton a downlink CC that is configured with transmission mode 3, 4 or 8. UE120 x may generate one ACK/NACK bit for each transport block. Forexample, one ACK/NACK bit may used to acknowledge a data transmission ona CC configured in transmission mode 1, 2, 5, 6 or 7 and two ACK/NACKbits may be used to acknowledge a data transmission on a CC configuredin transmission mode 3, 4 or 8.

The number of ACK/NACK bits for acknowledging a transmission of one ormore transport blocks on a downlink CC may also be dependent on a DCIformat of a corresponding downlink grant. LTE supports a number of DCIformats. DCI format 1, 1A, 1B, 1C or 1D may be used to send a downlinkgrant for a transmission of one transport block and may thus beassociated with one ACK/NACK bit. DCI formats 2, 2A or 2B may be used tosend a downlink grant for a transmission of two transport blocks and maythus be associated with two ACK/NACK bits. A DCI format of a downlinkgrant may be associated with a particular number of transport blocks tosend on a downlink CC, which may be different from (e.g., fewer than)the number of transport blocks associated with a transmission modeconfigured for the downlink CC. For example, CCj may be configured witha transmission mode supporting two transport blocks but may be scheduledwith a downlink grant having a DCI format used with one transport block.In that case, eNB 110 x may send one transport block on CCx and UE 120 xmay generate one bit of ACK/NACK information to acknowledge the datatransmission on CCj.

In one example, UE 120 x may be configured with five downlink CCs formulti-carrier operation in FDD. In this case, in a given subframe, eNB110 x may send up to ten transport blocks on the up to five downlinkCCs, with up to two transport blocks per downlink CC. Up to ten ACK/NACKbits may be obtained for up to ten transport blocks, one ACK/NACK bitfor each transport block (up to 12 ACK/NACK bits may be obtained if DTXis explicitly signaled). UE 120 x may thus have N ACK/NACK bits for adata transmission over a set of M configured downlink CCs, where1≦M≦N≦10.

According to the present disclosure, techniques for determining thenumber of ACK/NACK bits for a data transmission on M downlink CCs in amulti-carrier wireless communication network are described. The numberof ACK/NACK bits for acknowledging a data transmission may be determinedin different manners depending on the availability of certaininformation. The number of ACK/NACK bits, in turn, may be used tocontrol transmission of ACK/NACK information. In one aspect, a downlinkassignment index (DAI) may be used to facilitate determination of thenumber of ACK/NACK bits for a data transmission on M downlink CCs. A DAImay be included in a downlink grant. The DAI may indicate the number ofdownlink CCs scheduled and it may also provide an indication of whichdownlink CCs are scheduled. UE 120 x can use information obtained fromthe DAI to detect missing downlink grants, facilitate more efficientACK/NACK feedback, and/or provide other advantages.

The total number of ACK/NACK bits for M configured CCs may be referredto as the ACK/NACK bitwidth, the ACK/NACK payload size, etc. TheACK/NACK bitwidth may be dependent on whether ACK/NACK bits fordifferent downlink CCs are ordered or non-ordered. The use of ordered ornon-ordered feedback may be configured for UE 120 x. For the non-orderedcase, ACK/NACK bits for the M configured CCs may be concatenated in apredetermined order, e.g., based on an index of each downlink CC. Forthe ordered case, ACK/NACK bits for the M configured CCs may beconcatenated by first considering ACK/NACK bits for the scheduled CCsand then considering ACK/NACK bits for the remaining CCs.

FIG. 6 shows an example of determining ACK/NACK bitwidth for the orderedand non-ordered cases. In this example, UE 120 x is configured with fivedownlink CCs (CC1-CC5). CC2 and CC5 are associated with 1-bit ACK/NACKfeedback (e.g., based on transmission mode and DCI format as previouslydiscussed). CC1, CC3 and CC4 are associated with 2-bit ACK/NACKfeedback. Only CC2, CC3 and CC4 are scheduled in a particular subframe.A set of bits to be encoded and sent as ACK/NACK feedback may bedetermined as follows:

-   -   Non-ordered case: ‘00’ (CC1)+1 bit (CC2)+2 bits (CC3)+2 bits        (CC4)+‘0’ (CC5)+zeros, or    -   Ordered case: 1 bit (CC2)+2 bits (CC3)+2 bits (CC4)+zeros.

ACK/NACK information may be sent on the PUCCH or PUSCH in a fixedpayload size. In this case, zero padding with a sufficient number ofzeros may be performed to obtain a set of bits of the proper payloadsize.

The non-ordered case may result in simpler operation since one or twoACK/NACK bits for each configured CC may be readily obtained from theACK/NACK feedback based on the CC index and the number of ACK/NACK bitsfor each configured CC. However, the ordered case may have betterefficiency since the ACK/NACK bits for the scheduled CCs are placedfirst and may thus result in fewer bits being used for ACK/NACKfeedback. In some examples, CSI and/or other information may bemultiplexed in the remaining bits of the payload after ACK/NACKinformation for the scheduled carriers is added.

Table 3 lists three DAI schemes for multi-carrier operation according tothe present disclosure. In the first scheme, a DAI is not included indownlink grants. In the second and third schemes, a DAI is supported andconveys different information. Determination of ACK/NACK bitwidth basedon each of the three schemes is described below.

TABLE 3 DAI Schemes Scheme Description First No DAI Downlink grant doesnot include DAI. Scheme Second DAI indicates number Downlink grantincludes DAI Scheme of scheduled CCs indicating number of downlink CCsscheduled in a subframe. Third DAI identifies Downlink grant includesDAI Scheme scheduled CCs indicating number of downlink CCs and whichdownlink CCs are scheduled in a subframe.

In the second scheme, the DAI indicates the number downlink CCs beingscheduled and may be set to a value within a range of 1 to M−1. In oneexample, the DAI may have a variable width, which may be dependent on M.For example, the DAI may include one bit for M=2, two bits for M=3 or 4,or three bits for M=5. In another example, the DAI may have a fixedwidth (e.g., of three bits) that is independent of M. The DAI may beincluded in a downlink grant for each scheduled CC or for only certainscheduled CCs.

In the third scheme, the DAI indicates the number of downlink CCs beingscheduled as well as an identifier of the scheduled CCs. The DAI may beincluded in a downlink grant for a scheduled CC and may indicate whichother downlink CCs (if any) are also scheduled. With the third scheme,the DAI may be defined in different manners.

In one variation of the third scheme, the DAI may have a variable widththat is dependent on M. The number of bits used for the DAI may besmaller than the number of configured CCs. For example, if M=1, then theDAI may be omitted. If M=2, then the DAI may comprise one bit and may beset to (i) a first value (e.g., ‘0’) to indicate one downlink CC beingscheduled, which is the downlink CC associated with the downlink grantincluding the DAI, or (ii) a second value (e.g., ‘1’) to indicate twodownlink CCs being scheduled. If M=3, then the DAI may comprise two bitsand may be set to (i) a first value (e.g., ‘00’) to indicate onedownlink CC being scheduled, (ii) a second value (e.g., ‘01’) toindicate a first remaining downlink CC also being scheduled, (iii) athird value (e.g., ‘10’) to indicate a second remaining downlink CC alsobeing scheduled, or (iv) a fourth value (e.g., ‘11’) to indicate allthree downlink CCs being scheduled.

To further illustrate matters, consider the case of three configured CCs(CCx, CCy and CCz). The eNB may set the DAI in a downlink grant for CCxto the second value to indicate that CCy is scheduled, or to the thirdvalue to indicate that CCz is scheduled. If M=4, a 3-bit DAI may beutilized. The DAI may be set to (i) a first value to indicate onedownlink CC being scheduled, (ii) a second, a third, or a fourth valueto indicate one other downlink CC also being scheduled among the threeremaining downlink CCs, (iii) a fifth, a sixth, or a seventh value toindicate two other downlink CCs also being scheduled among the threeremaining downlink CCs, or (iv) an eight value to indicate all fourdownlink CCs being scheduled.

Continuing with this example, a 4-bit DAI may be utilized when M=5. TheDAI may be set to (i) a first value to indicate one downlink CC beingscheduled, (ii) a value within the 2nd through 5th value to indicate oneother downlink CC also being scheduled among the four remaining downlinkCCs, (iii) a value within the 6th through 11th value to indicate twoother downlink CCs also being scheduled among the four remainingdownlink CCs, (iv) a value within the 12th through 14th value toindicate three other downlink CCs also being scheduled among the fourremaining downlink CCs, or (v) a 15th value to indicate all fivedownlink CCs being scheduled. When the variable width DAI of the thirdscheme is utilized, UE 120 x may be able to determine how many downlinkCCs and which downlink CCs are scheduled based on the DAI in onedownlink grant for one scheduled CC.

In another variation of the third scheme, the DAI may comprise a bitmapof M−1 bits, with one bit for each remaining downlink CC (not includingthe downlink CC on which the PDCCH is received). The bit for eachremaining downlink CC may be set to a first value (e.g., ‘0’) toindicate the downlink CC is not scheduled or to a second value (e.g.,‘1’) to indicate the downlink CC is scheduled. The number of downlinkCCs being scheduled may be equal to 1 (for the downlink CC associatedwith a downlink grant carrying the DAI) plus the number of ones in thebitmap.

FIG. 7 shows an example of the DAI for the bitmap variation of the thirdscheme. In this example, the DAI is included in a downlink grant for aPDSCH transmission on downlink CC2 and comprises a bitmap of M−1 bitsfor M−1 other downlink CCs. The bit for CC1 is set to ‘0’ to indicateCC1 not being scheduled, the bit for CC3 is set to ‘1’ to indicate CC3being scheduled, etc. UE 120 x may receive the DAI in a downlink grantfor a PDSCH transmission on one scheduled CC. Based on the DAI, UE 120 xcan determine all scheduled CCs based on the DAI in the receiveddownlink grant, even if it does not detect the downlink grants for allof the other scheduled CCs.

In another variation, the DAI may comprise a limited number of bits, andonly some scheduled CCs may be identified by the DAI. For example, theDAI may comprise two bits (instead of M−1 bits) even when more than twodownlink CCs are scheduled. In this variation, the downlink PCC may begiven higher priority than the downlink SCCs. For M=3, the DAI canidentify each downlink CC that is scheduled, as described above. ForM=4, the DAI in a downlink grant for the PCC may include one bitcovering two SCCs and another bit covering the last SCC. The DAI in adownlink grant for an SCC may include one bit covering the PCC andanother bit covering the other two SCCs. For M=5, the DAI in a downlinkgrant for the PCC may include one bit covering two SCCs and another bitcovering the last two SCCs. The DAI in a downlink grant for an SCC mayinclude one bit covering the PCC and another bit covering the otherthree SCCs. In this variation, two or more entries may share the sameDAI value. For example, the same DAI value (e.g., ‘00’) may be used forthe case of one scheduled CC and another case of four scheduled CCs,since the probability of confusion between these two cases may be small.This may allow for a tradeoff between overhead and ambiguity in theinformation provided by the DAI.

As described herein, further variations of the DAI in the second andthird schemes may also utilized. Additionally, the DAI may conveydifferent information depending upon the CC configuration for aparticular UE. For example, different DAI schemes may be utilized inconnection with different CC configurations or in support of differentUEs.

A DAI indicating the number of scheduled CCs and/or identifying thescheduled CCs may be sent in various manners. In one example, the DAImay be included in each downlink grant sent on the PDCCH for eachscheduled CC. In another example, the DAI may be included only indownlink grants for the downlink PCC. In yet another example, the DAImay be included in one or more downlink grants for one or moredesignated CCs, e.g., the first and last CCs. Additionally oralternatively, a DAI for downlink data transmission may be included inan uplink grant sent on the PDCCH. This design may provide additionalprotection against missed detection of the PDCCH by a UE.

The ACK/NACK bitwidth for M configured CCs may be determined in variousmanners for the three schemes listed in Table 3. Some exemplary designsof determining the ACK/NACK bitwidth are described below.

For the first scheme with no DAI, an exemplary ACK/NACK bitwidth for Mconfigured CCs may be determined as follows:

$\begin{matrix}{{n_{HARQ} = {\sum\limits_{C \in {{Configured}\_ {Set}}}n_{C}}},} & {{Eq}\mspace{14mu} (1)}\end{matrix}$

where n_(C) is the number of ACK/NACK bits for downlink CC C,

-   -   n_(HARQ) is the total number of ACK/NACK bits for M configured        CCs, and Configured_Set denotes a set of configured CCs.

n_(HARQ) is the ACK/NACK bitwidth for the M configured CCs. n_(HARQ) inequation (1) may be the same for both the ordered and non-ordered cases.

In another design, the ACK/NACK bitwidth for cases where no DAI isprovided may be determined as follows:

$\begin{matrix}{{n_{HARQ} = {\sum\limits_{C \in {{Activated}\_ {Set}}}n_{C}}},} & {{Eq}\mspace{14mu} (2)}\end{matrix}$

where Activated_Set denotes a set of activated CCs. The set of activatedCCs may include all or a subset of the M configured CCs.

In yet another design, in the absence of DAI, the ACK/NACK bitwidth maybe determined as follows:

$\begin{matrix}{{n_{HARQ} = {\sum\limits_{C \in {{Detected}\_ {Set}}}n_{C}}},} & {{Eq}\mspace{14mu} (3)}\end{matrix}$

where Detected_Set denotes a set of detected CCs. The set of detectedCCs may include all or a subset of the M configured CCs. Detected CCsmay be determined as described above.

As shown in equation (3), when the detected CCs are known from thedetection of downlink grants, the ACK/NACK bitwidth may be determinedbased on the ACK/NACK bits for only the detected CCs. This may result ina smaller and more accurate ACK/NACK bitwidth.

n_(C) in equations (1) to (3) may be defined in the same manner ordifferent manners. For example, n_(C) in equation (1) may be determinedbased on a transmission mode of each CC in the configured set, whereasn_(C) in equation (3) may be determined based on a DCI format of adownlink grant for the CCs in the detected set.

For the second scheme with DAI indicating the number of scheduled CCs,the ACK/NACK bitwidth for M configured CCs may be determined differentlyfor the ordered and non-ordered cases described above. In one example ofthe non-ordered case, ACK/NACK bitwidth may be determined based on theconfigured CCs, as shown in equation (1). Although only a subset of theM configured CCs may be scheduled, the DAI may not indicate whichparticular downlink CCs are scheduled. Hence, the UE may determined anACK/NACK bitwidth based on a number of ACK/NACK bits for all Mconfigured CCs.

When ordered feedback is used with the second scheme, ACK/NACK bitwidthmay be determined in different manners. In one example, the ACK/NACKbitwidth may be determined as follows:

$\begin{matrix}{n_{HARQ} = \left\{ \begin{matrix}n_{C} & {{{for}\mspace{14mu} {DAI}} = 1} \\{{DAI} \star {\max \left( n_{C} \right)}} & {{{for}\mspace{14mu} 1} < {DAI} < M} \\{\sum\limits_{C \in {{Configured}\_ {Set}}}n_{C}} & {{{for}\mspace{14mu} {DAI}} = M}\end{matrix} \right.} & {{Eq}\mspace{14mu} (4)}\end{matrix}$

In equation (4), the ACK/NACK bitwidth varies according to the number ofscheduled CCs and may be equal to the number of ACK/NACK bits for the CCon which PDCCH is transmitted when one downlink CC is scheduled (withDAI=1). The ACK/NACK bitwidth may be equal to the total number ofACK/NACK bits for all M configured CCs if all configured CCs arescheduled (with DAI=M). The ACK/NACK bitwidth and may be equal to thenumber of scheduled CCs times the maximum number of ACK/NACK bits perscheduled CC if two to M−1 downlink CCs are scheduled. SinceDAI*max(n_(C)) may be larger than Σn_(C), n_(HARQ) may be limited toΣn_(C).

In another example, when ordered feedback is used with the secondscheme, the ACK/NACK bitwidth may be determined as follows:

$\begin{matrix}{\mspace{79mu} {n_{HARQ} = \left\{ \begin{matrix}n_{C} & {{{for}\mspace{14mu} {DAI}} = 1} \\n_{X} & {{{for}\mspace{14mu} 1} < {DAI} < M} \\{\sum\limits_{C \in {{Configured}\_ {Set}}}n_{C}} & {{{for}\mspace{14mu} {DAI}} = M}\end{matrix} \right.}} & {{Eq}\mspace{14mu} (5)} \\{n_{X} = {{\max \left\{ {n_{1},\ldots \mspace{11mu},{\cdot n_{M - {DAI} + 1}}} \right\}} + {\max \left\{ {n_{2},\ldots \mspace{11mu},{\cdot n_{M - {DAI} + 2}}} \right\}} + \ldots + {\max \left\{ {n_{DAI},\ldots \mspace{11mu},{\cdot n_{M}}} \right\}}}} & {{Eq}\mspace{14mu} (6)}\end{matrix}$

In equation (6), for a given DAI value, the first scheduled CC is amongdownlink CCs 1 through M−DAI+1, the second scheduled CC is amongdownlink CCs 2 through M−DAI+2, and so on, and the last scheduled CC isamong downlink CCs DAI to M. This observation is exploited in equation(6) to possibly reduce the ACK/NACK bitwidth. Since n_(X) may be largerthan Σn_(C), n_(HARQ) may be limited to Σn_(C). For example, UE 120 xmay be configured with five downlink CCs associated with 1, 2, 1, 2 and1 ACK/NACK bits based on the transmission modes configured for thesedownlink CCs. In this example, Σn_(C) is equal to 7 bits. If fourdownlink CCs are scheduled and DAI=4, then n_(X) is equal to 8 and islarger than Σn_(C). In this case, n_(HARQ) may be limited to 7.Conversely, if three downlink CCs are scheduled and DAI=3, then n_(X) isequal to 6 and is smaller than Σn_(C). In this case, n_(HARQ) is equalto 6. For the case of two downlink CCs, n_(HARQ) may be set to Σn_(C).

For the third scheme in which a DAI identifies both the number andidentity of the scheduled CCs, the ACK/NACK bitwidth for M configuredCCs may be determined as follows:

$\begin{matrix}{{n_{HARQ} = {\sum\limits_{C \in {{Scheduled}\_ {Set}}}n_{C}}},} & {{Eq}\mspace{14mu} (7)}\end{matrix}$

where Scheduled_Set denotes a set of scheduled CCs.

As shown in equation (7), when the scheduled CCs are known from the DAI,the ACK/NACK bitwidth may be determined based on the ACK/NACK bits foronly the scheduled CCs. For example, the number of ACK/NACK bits foreach scheduled CC may be determined based on (i) the transmission modeconfigured for the scheduled CC or (ii) the DCI format of a downlinkgrant for the scheduled CC. This would increase efficiency byfacilitating a more accurate determination of the ACK/NACK bitwidth.

Table 4 summarizes the determination of ACK/NACK bitwidth for the threeschemes listed in Table 3.

TABLE 4 ACK/NACK Bitwidth Determination Non-ordered Ordered Scheme CaseCase Comments No DAI Σn_(C) over Same as Fixed ACK/NACK configured CCsnon-ordered overhead if or detected CCs case sum over configured CCs.DAI indicates Σn_(C) over Equation (4) Ordered ACK/NACK number ofconfigured CCs or Equations feedback may be scheduled CCs (5) & (6) moreefficient. DAI identifies Σn_(C) over Same as Minimum ACK/ scheduled CCsscheduled CCs non-ordered NACK overhead. case

In one example of operation, which may be applicable for all threeschemes listed in Table 3, UE 120 x may determine the total number oftransport blocks received on the M configured CC. UE 120 x may detectfor downlink grants intended for UE 120 x and may determine the DCIformat of each detected downlink grant. UE 120 x may receive onetransport block on each downlink CC associated with a downlink granthaving a DCI format supporting one transport block. UE 120 x may receivetwo transport blocks on each downlink CC associated with a downlinkgrant having a DCI format supporting two transport blocks. UE 120 x maydetermine the total number of transport blocks received on allconfigured CCs as follows:

$\begin{matrix}{{n_{TB} = {\sum\limits_{C \in {{Detected}\_ {Set}}}n_{{TB},C}}},} & {{Eq}\mspace{14mu} (8)}\end{matrix}$

where n_(TB,C) is the number of transport blocks received on downlink CCC, and

n_(TB) is the total number of transport blocks received on allconfigured CCs.

The total number of transport blocks received on all configured CCs(n_(TB)) may be referred to as a total transport block count. UE 120 xmay determine the ACK/NACK bitwidth based on the total transport blockcount, e.g., one ACK/NACK bit for each received transport block, so thatn_(HARQ)=n_(TB). The number of transport blocks received on eachdownlink CC may be equal to or less than the number of transport blocksfor a transmission mode configured for that downlink CC. Hence, thetotal transport block count determined based on detected downlink grantsmay be equal to or less than the ACK/NACK bitwidth determined based ontransmission modes of the configured CCs or detected CCs. The CK/NACKbitwidth determined based on transmission modes may be considered as (i)the maximum possible number of ACK/NACK bits for M configured CCs, or(ii) the total number of bits available to send ACK/NACK information forthe M configured CCs. The total transport block count may be consideredas the actual number of ACK/NACK bits to send for the M configured CCs.

UE 120 x may send ACK/NACK information for M configured CCs on eitherthe PUCCH or PUSCH in a given subframe, e.g., depending on whether UE120 x is also scheduled for data transmission on the uplink in thesubframe. The ACK/NACK bitwidth and/or the total transport block countmay be used for various purposes such as one or more of the following:

-   -   Power control of ACK/NACK information sent on the PUCCH,    -   Determination of a number of resource elements for sending        ACK/NACK information on the PUSCH,    -   Determination of an ACK/NACK feedback scheme for sending        ACK/NACK information on the PUCCH,    -   Determination of a code rate and/or a coding scheme for sending        ACK/NACK information on the PUCCH or PUSCH, and    -   Determination of available bits for sending CSI and/or other        information with ACK/NACK information on the PUCCH or PUSCH.

A multi-carrier UE may also perform power control for the PUCCH based onthe ACK/NACK bitwidth or the total transport block count. In general,the signal-to-noise ratio (SNR) needed to reliably receive an ACK/NACKtransmission may be dependent on the ACK/NACK bitwidth, or the number ofACK/NACK bits to send. The ACK/NACK bitwidth may, in turn, be dependenton the number of scheduled CCs. Since the required SNR may vary by morethan 3 dB, e.g., for one scheduled CC versus five scheduled CCs,accurate determination of ACK/NACK bitwidth is important for efficientoperation in a multi-carrier network.

The transmit power to use to send ACK/NACK information and possibly CSIon the PUCCH may be determined as follows:

P _(PUCCH) =f{h(n _(CSI) ,n _(HARQ))},  Eq (9)

where n_(CSI) is the number of CSI bits to send with ACK/NACKinformation,

h(.) is a predefined function described in LTE,

f(.) is another predefined function described in LTE, and

P_(PUCCH) is the transmit power for the PUCCH.

As shown in equation (9), the transmit power of the PUCCH may bedependent on the number of ACK/NACK bits to send, or ACK/NACK bitwidth.The ACK/NACK bitwidth for power control of the PUCCH may be determinedin various manners. In a first example, which may be referred to as aslow option, ACK/NACK bitwidth may be determined based on the configuredCCs for UE 120 x, which may be computed as shown in equation (1) for thefirst scheme. In a second example, which may be referred to as a mediumoption, the ACK/NACK bitwidth may be determined based on the activatedCCs for UE 120 x, which may be computed as shown in equation (2) for thefirst scheme. In a third example, which may be referred to as a fastoption, the ACK/NACK bitwidth may be determined based on the detectedCCs carrying data on the PDSCH, which may be computed as shown inequation (3) for the first scheme.

Other approaches may also include determining ACK/NACK bitwidth based onthe scheduled CCs. For example, ACK/NACK bitwidth may be determined overthe set of scheduled CCs as when the DAI identifies both number andidentity of each scheduled CC, e.g., as shown in equation (7).Alternatively, the ACK/NACK bitwidth may be determined based on thetotal number of transport blocks received on the M configured CCs, e.g.,as shown in equation (8). The ACK/NACK bitwidth may also be depend uponwhether an ordered or non-order feedback configuration is utilized aspreviously discussed.

The slow and medium options may result in “over” power control since UE120 x may be scheduled on fewer downlink CCs than the configured CCs. UE120 x may then use higher transmit power for the PUCCH than necessary.The fast option may result in “under” power control since UE 120 x maymiss detecting downlink grants on the PDCCH for some scheduled CCs. UE120 x may then use less transmit power for the PUCCH than necessary.However, the likelihood of missing detection of downlink grants may below (e.g., typically around 1% for each downlink CC). Hence, the underpower control issue may not be severe.

Power control of the PUCCH can be performed by eNB 110 x to mitigate thepotential for a power control mismatch as described above. For the slowand medium options, eNB 110 x may determine a power down command basedon the difference between the number of scheduled CCs and the number ofconfigured or activated CCs. For the fast option, eNB 110 x maydetermine a power up command based on the difference between an estimateof the number of detected CCs by UE 120 x (which is unknown to eNB 110x) and the number of scheduled CCs (which is known to eNB 110 x). Forall options, eNB 110 x may send a power control command (which may be apower down command or a power up command) to UE 120 x. The power controlcommand may be sent via embedded information in a downlink grant, or viagroup power control in DCI formats 3/3A, or via some other mechanism. UE120 x may adjust its computed transmit power for the PUCCH based on thepower control command.

For transmissions on PUSCH, the number of resource elements to use tosend ACK/NACK information (which may be referred to as the requirednumber of PUSCH resource elements) may be determined based on theACK/NACK bitwidth or the total transport block count. In one example, UE120 x may determine a number of PUSCH resource elements based on theACK/NACK bitwidth for the configured CCs, which may be computed as shownin equation (1) for the no-DAI case. In a second example, UE 120 x maydetermine the number of PUSCH resource elements for acknowledging a datatransmission based on the ACK/NACK bitwidth for the activated CCs, whichmay be computed as shown in equation (2) for the no-DAI case. In a thirdexample, UE 120 x may determine the number of PUSCH resource elementsbased on the ACK/NACK bitwidth for the detected CCs, which may becomputed as shown in equation (3) for the no-DAI case. In otherexamples, UE 120 x may determine the number of PUSCH resource elementsbased on (i) the ACK/NACK bitwidth for the scheduled CCs, which may bedetermined as shown in equation (7) for the third scheme, or (ii) thetotal number of transport blocks received on the M configured CCs, whichmay be determined as shown in equation (8).

In each of the above examples, the number of PUSCH resource elements foracknowledging a data transmission may be reserved or set aside fromamong all resource elements available on the PUSCH. UE 120 x may sendACK/NACK information on the reserved resource elements on the PUSCH.Data and/or other information may be sent on the remaining resourceelements on the PUSCH. eNB 110 x may configure UE 120 x for a particularresource utilization scheme on the PUSCH to avoid misalignment.

When UE 120 x determines that ACK/NACK information is sent on the PUCCH,ACK/NACK feedback scheme may be determined based on the ACK/NACKbitwidth or the total transport block count. For example, up to two bitsof ACK/NACK information may be sent on the PUCCH based on PUCCH format1a or 1b. PUCCH format 1a supports transmission of one ACK/NACK bit onthe PUCCH and may be used when one downlink CC is scheduled. PUCCHformat 1b supports transmission of two ACK/NACK bits on the PUCCH andmay be used when two transport blocks are scheduled on one downlink CCor one transport block is scheduled on each of two downlink CCs.

Up to four bits of ACK/NACK information may be sent on the PUCCH basedon PUCCH format 1b and channel selection. In this example, two signalingbits, b₀ and b₁, may be sent on one of multiple PUCCH resourcesavailable for use by UE 120 x. The values of bits by and b₁ as well asthe selected PUCCH resource may be determined based on the ACK/NACKinformation.

When UE 120 x is configured for PUCCH format 3, which utilizesDFT-spread OFDM (DFT-S-OFDM), more than four bits of ACK/NACKinformation may be sent on the PUCCH. For PUCCH format 3, n_(HARQ) bitsof ACK/NACK information may be transformed to the frequency domain basedon a DFT and mapped to resource elements in one or more resource blocksused for ACK/NACK transmission. SC-FDMA symbols may be generated basedon the mapped symbols.

PUCCH format 3 may be used to send ACK/NACK information regardless ofthe number of downlink CCs. This approach allows the same PUCCH formatto be used irrespective of the number of configured CCs or scheduledCCs. For example, eNB 110 x may process the ACK/NACK information basedon one PUCCH format (instead of having to perform blind detection fordifferent PUCCH formats). Additionally, using the additional payloadavailable with PUCCH format 3, UE 120 x can multiplex CSI and/or otherinformation with ACK/NACK information. PUCCH format 3 may also be usedto send only CSI, which may simplify operation of eNB 110 x to detectfor CSI and/or ACK/NACK information from UE 120 x.

All or a subset of the designs described above may be used to sendACK/NACK information on the PUCCH. For example, PUCCH format 1a/1b andPUCCH format 3 may be used as appropriate. The ACK/NACK bitwidth forselecting a suitable ACK/NACK feedback scheme may be determined based onthe configured CCs, the activated CCs, the detected CCs, or thescheduled CCs.

UE 120 x can select a code rate and/or a coding scheme for ACK/NACKinformation based on the ACK/NACK bitwidth or the total transport blockcount. The ACK/NACK information may be encoded based on a block code(e.g., a Reed-Muller code) of a particular code rate to obtain codeddata. The coded data may be further processed and sent on the PUCCH orPUSCH. Selection of a suitable code rate may be especially relevant forACK/NACK information sent on the PUCCH based on PUCCH format 3 as wellas for ACK/NACK information multiplexed with data on the PUSCH.

As described above, the number of bits of ACK/NACK information(n_(HARQ)) may be variable and dependent on the ACK/NACK bitwidth. Thenumber of bits of coded data (n_(PAYLOAD)), on the other hand, may befixed and dependent on the available payload for ACK/NACK information onthe PUCCH or PUSCH. The code rate may be selected based on n_(HARQ) andn_(PAYLOAD) so that the coded data can be sent in the available payloadon the PUCCH or PUSCH. The code rate may be determined based on theACK/NACK bitwidth for the configured CCs, the activated CCs, thedetected CCs, or the scheduled CCs. Selecting the code rate based on theACK/NACK bitwidth for the configured CCs may ensure that eNB 110 x andUE 120 x will both use the same code rate. Selecting the code rate basedon the ACK/NACK bitwidth for the activated CCs or the detected CCs mayprovide better performance with an increased possibility of misalignmentbetween the code rate determined by eNB 110 x and the code ratedetermined by UE 120 x. In one example, eNB 110 x performs decoding fordifferent possible code rates to address possible misalignments. Fastadaptation based on the detected CCs may enable the use of differentbasis sequences for the block code.

The number of bits available to send CSI and/or other information mayalso be determined based on the ACK/NACK bitwidth or the total transportblock count. ACK/NACK information, CSI, and/or other information may bemultiplexed, and the resultant UCI may be sent on the PUCCH or PUSCH.One PUCCH or one PUSCH can support feedback of both ACK/NACK informationand CSI simultaneously, which may be jointly encoded. The availablepayload for UCI on the PUCCH or PUSCH may be fixed and may be denoted asn_(PAYLOAD). For example, up to 13 information bits may be sent on thePUCCH based on PUCCH format 3.

In one example, the number of bits available to send CSI and/or otherinformation, n_(CSI), is determined based on the ACK/NACK bitwidth orthe total transport block count, as follows:

n _(CSI) =n _(PAYLOAD) −n _(HARQ).  Eq (10)

n_(HARQ) in equation (10) may be determined based on the ACK/NACKbitwidth for the configured CCs, the activated CCs, or the detected CCs,or the scheduled CCs. n_(HARQ) in equation (10) may also be determinedbased on the total transport block count. n_(HARQ) may be determinedbased on the DAI, if available. n_(HARQ) may also be dependent onwhether the ACK/NACK information is ordered or not ordered.

eNB 110 x may control the number of ACK/NACK bits in view of potentialfeedback overhead for CSI. For example, eNB 110 x may schedule up tofive downlink CCs in a subframe if there is only 4-bit wideband CSIfeedback to report with the ACK/NACK information. Similarly, eNB 110 xmay schedule one or two downlink CCs with 2-bit ACK/NACK feedback in aparticular subframe when 11-bit CSI feedback is expected and would bemultiplexed with the ACK/NACK information. eNB 110 x may thus schedule anumber of downlink CCs such that the total overhead for ACK/NACKfeedback and CSI feedback can fit in the available payload for UCI.

Table 5 lists four exemplary designs of sending ACK/NACK information.Each of the four ACK/NACK designs is described in further detail below.

TABLE 5 ACK/NACK Designs ACK/NACK Design Description First No DAI No DAIfor downlink CCs. Design CSI not multiplexed with ACK/NACK. Second NoDAI No DAI for downlink CCs. Design CSI can be multiplexed withACK/NACK. Third DAI indicates DAI indicates number of downlink Designnumber of CCs scheduled in a subframe. scheduled CCs CSI can bemultiplexed with ACK/NACK. Fourth DAI identifies DAI indicates number ofDesign scheduled CCs downlink CCs and identifies the scheduled CCs in asubframe. CSI can be multiplexed with ACK/NACK.

In the first ACK/NACK design, DAI is not used for downlink CCs (but maybe used for downlink subframes in TDD as described below). The ACK/NACKbitwidth or the total transport block count for power control of thePUCCH carrying ACK/NACK information may be determined based on detectedCCs, e.g., as shown in equation (3) or (8). The ACK/NACK bitwidth or thetotal transport block count for determining the number of resourceelements for sending ACK/NACK information on the PUSCH may be determinedbased on configured CCs, e.g., as shown in equation (1). When DAI is notavailable, UE 120 x may be configured to drop CSI when it collides withACK/NACK information in a subframe and the ACK/NACK informationcomprises more than two bits. In particular, UE 120 x may not multiplexCSI with ACK/NACK information when DAI is not available and itdetermines that there are more than two bits of ACK/NACK feedback. Ifthere is only one or two ACK/NACK bits, then ACK/NACK information may bemultiplexed with CSI as described in LTE Release 8.

In situations where DAI is not utilized, it is possible to reduce DCIoverhead. However, without the additional information about scheduledCCs, there may be errors in determining the ACK/NACK bitwidth, which mayresult in some errors in determination of transmit power for the PUCCHor the number of resource elements in the PUSCH to send ACK/NACKinformation. Determining the ACK/NACK bitwidth based on the detected CCsfor PUCCH power control and based on the configured CCs for countingresource elements on the PUSCH as described herein may mitigate theimpact of such errors.

The second ACK/NACK design also does not utilize DAI but provides formultiplexing ACK/NACK with CSI on the PUCCH or PUSCH. The ACK/NACKbitwidth or the total transport block count for ascertaining the numberof bits available to send CSI and/or other information may be determinedbased on the configured CCs, the activated CCs, or the detected CCs.Allowing CSI to be multiplexed with ACK/NACK information may result inless frequent dropping of CSI, which may improve performance of datatransmission.

In the third ACK/NACK design, a DAI may be included in a downlink grantand may indicate the number of downlink CCs scheduled in a subframe,i.e., the total number of PDSCH transmissions. UE 120 x may performvarious functions based on the DAI. For example, UE 120 x may determinethe ACK/NACK bitwidth based on the DAI, as shown in equation (4) or (5).UE 120 x may then determine the transmit power for sending ACK/NACKinformation on the PUCCH, the number of resource elements for sendingACK/NACK information on the PUSCH, the ACK/NACK feedback scheme forsending ACK/NACK information, the number of bits available to send CSIand/or other information, the code rate for encoding ACK/NACKinformation, etc. based on the ACK/NACK bitwidth or the total transportblock count. UE 120 x may also utilize the DAI to reduce PDCCH blinddetection and lower the associated probability of false alarms. Inparticular, UE 120 x may utilize explicit information on the number ofscheduled CCs obtained from the DAI to determine when to stop decodingthe PDCCH and avoid processing downlink CCs that do not include anydownlink grants.

In the fourth ACK/NACK design, a DAI may be included in a downlink grantand may indicate both the number of downlink CCs scheduled in a subframeand the identify the scheduled CCs, i.e., the total number and positionof the scheduled CCs. CC identity may be signaled, for example, when thebits of the DAI correspond to different ones of the CCs configured forUE 120 x. Using information from the DAI, UE 120 x may perform variousfunctions. For example, UE 120 x may accurately determine the ACK/NACKbitwidth based on the scheduled CCs indicated by the DAI, as shown inequation (7). UE 120 x may also accurately determine the transmit powerfor sending ACK/NACK information on the PUCCH, the number of resourceelements for sending ACK/NACK information on the PUSCH, the ACK/NACKfeedback scheme for sending ACK/NACK information, the number of bitsavailable to send CSI and/or other information, the code rate forencoding ACK/NACK information, etc. based on the ACK/NACK bitwidth orthe total transport block count. UE 120 x may also utilize the DAI todetermine which downlink CCs to decode the PDCCH for downlink grants andwhich downlink CCs to skip.

Table 6 summarizes transmission of ACK/NACK information on the PUCCH forthe three schemes listed in Table 3.

TABLE 6 ACK/NACK Transmission on PUCCH Scheme Description No DAI PUCCHpower control based on detected CCs. DAI indicates PUCCH power controlbased on DAI. number of Some leftover room for multiplexing scheduledCCs CSI with ACK/NACK. Improved PDCCH blind detection and false alarmprobability. DAI identifies PUCCH power control based on DAI. scheduledCCs Accurate ACK/NACK bitwidth determination. Maximum leftover room formultiplexing CSI with ACK/NACK. Improved PDCCH blind detection and falsealarm probability.

Table 7 summarizes transmission of ACK/NACK information on the PUSCH forthe three schemes listed in Table 3.

TABLE 7 ACK/NACK Transmission on PUSCH Scheme Description No DAI Numberof resource elements for ACK/NACK information determined based onconfigured CCs or activated CCs. DAI indicates Number of resourceelements for ACK/NACK number of information determined based on DAI.scheduled CCs Improved PDCCH blind detection and false alarmprobability. DAI identifies Number of resource elements for ACK/NACKscheduled CCs information determined based on DAI. Accurate ACK/NACKbitwidth determination. Improved PDCCH blind detection and false alarmprobability.

UE 120 x may be configured with semi-persistent scheduling (SPS) on thedownlink. For SPS, UE 120 x may be semi-statically configured withpertinent parameters for data transmission on a downlink CC, and eachPDSCH transmission may occur without sending a downlink grant on thePDCCH. SPS may be supported on only the downlink PCC or on any downlinkCC configured for UE 120 x.

When SPS is present (possibly on only the downlink PCC), misalignmentbetween eNB 110 x and UE 120 x may occur even if a DAI is present indownlink grants sent on downlink SCCs. For example, UE 120 x may beconfigured with two downlink CCs, with CC1 being a PCC and CC2 being anSCC. UE 120 x may be configured for SPS on the PCC without DAI and maybe dynamically scheduled on the SCC with DAI. If UE 120 x fails todetect the PDCCH for CC2, it may not know whether there is (i) only anSPS transmission on CC1, or (ii) both an SPS transmission on CC1 and adynamically scheduled transmission on CC2, or (iii) dynamicallyscheduled transmissions on both CC1 and CC2 (with the dynamicallyscheduled transmission on CC1 superseding an SPS transmission).

The situation described above may be addressed in various manners. Inone example, UE 120 x may behave as if the DAI is not included indownlink grants. UE 120 x may then perform PUCCH power control based ondetected CCs, determine the number of PUSCH resource elements based onconfigured CCs, etc. In another example, the DAI may include informationfor the PCC regardless of whether an SPS transmission or a dynamicallyscheduled transmission is sent on the PCC. In yet another example, theDAI may exclude information for the PCC if it has an SPS transmissionand may include information for the PCC if it has a dynamicallyscheduled transmission. An SPS transmission on the PCC may be associatedwith a fixed bitwidth (e.g., 1 bit) and a fixed location on the PUCCH orPUSCH if there is no dynamic scheduling transmission on the PCC.Otherwise, the DAI may include information for the PCC if it has adynamically scheduled transmission. Dynamically scheduled transmissionmay supersede SPS transmission when they conflict. In each case, UE 120x may perform PUCCH power control, determine the number of PUSCHresource elements, etc., as described above based on the availability ofthe DAI (or lack thereof).

In the third scheme shown in Table 3, a DAI may be included in eachdownlink grant and may identify all scheduled CCs. This arrangement isshown in FIG. 7. With information from the DAI, UE 120 x may obtainknowledge of the scheduled CCs as long as at least one downlink grant isreceived in a particular subframe. UE 120 x may determine the ACK/NACKbitwidth based on the number of ACK/NACK bits for each scheduled CC,e.g., as shown in equation (7).

It may be desirable for UE 120 x to send DTX to indicate a downlinkgrant/PDCCH that is not detected by UE 120 x. For example, UE 120 x maydetermine that CCx is scheduled based on the DAI included with adownlink grant received on CCy. However, UE 120 x may not detect adownlink grant for a PDSCH transmission on CCx. In that case, dependingupon its configuration, UE 120 x signals DTX for CCx, and eNB 110 x mayuse the DTX feedback to improve transmission of the PDCCH for CCx.

Unused bits may be used to convey DTX as follows. A given downlink CC,CCj, may be configured with a transmission mode supporting two transportblocks (e.g., a MIMO mode) and may be associated with two ACK/NACK bits.However, in a particular subframe, CCj may be scheduled with atransmission of one transport block (e.g., a SIMO mode). Only oneACK/NACK bit may needed to acknowledge the transmission on CCj. Theunused bit allocated based on the transmission mode may be used toconvey whether or not there is a missing downlink grant/PDCCH based uponinformation from the DAI. Unused bits may also be referred to asleftover bits, orphan bits, etc. Unused bits for multiple downlink CCsmay be used jointly to convey more information to eNB 110 x, e.g., toconvey which particular downlink grant/PDCCH is not detected by UE 120x.

In one example of reusing ACK/NACK bits, UE 120 x may be configured withthree downlink CCs, which may include CC1, CC2 and CC3. All threeconfigured CCs may be associated with transmission modes supporting twotransport blocks, for which two ACK/NACK bits are potentially needed foracknowledging a corresponding PDSCH transmission. eNB 110 x may scheduletwo of the configured CCs in a given subframe, with CC1 being scheduledwith DCI format 1 A for one transport block, and CC3 being scheduledwith DCI format 2 for two transport blocks. Four ACK/NACK bits may beavailable for the two scheduled CCs based on their transmission modes.However, for the data transmission described above, only three ACK/NACKbits may be generated, or one ACK/NACK bit for CC1 and two ACK/NACK bitsfor CC3. In that case, one unused bit would be available to UE 120 x forconveying DTX for one CC. The unused bit may, for example, be used toconvey DTX for CC3 and may be set to a first value (e.g., ‘0’) if adownlink grant/PUCCH for CC3 is received, or to a second value (e.g.,‘1’) if the downlink grant/PUCCH for CC3 is not received based oninformation about scheduled CCs obtained from the DAI. The four ACK/NACKbits may then be sent as follows:

-   -   Send {x100} to inform eNB 110 x that the downlink grant for CC3        is missing, or    -   Send {x0yz} to inform eNB 110 x that the downlink grant for CC3        is detected,        where x is an ACK/NACK bit for CC1, y and z are two ACK/NACK        bits for CC3, and x, y and z may each have a value of ‘0’ or        ‘1’.

In general, 12 bits may be used to convey ACK, NACK, or DTX for fivedownlink CCs. UE 120 x may be configured to report DTX whenever unusedbits are available, or to report DTX upon the occurrence or certainconditions. For example, UE 120 x may report DTX only if the number ofconfigured or scheduled CCs is less than four (in order to fit into a10-bit ACK/NACK payload), or only if two downlink CCs are configured,etc.

A DAI may also be used to convey information about scheduled subframesin TDD. For example, 2-bit DAI may be included in a downlink grant sentbased on DCI format 1, 1A, 1B, 1D, 2, 2A or 2B in LTE. The 2-bit DAI maybe sent in subframe n and may indicate the accumulative number ofPDCCH(s) with assigned PDSCH transmission(s) and PDCCH indicating SPSrelease, up to the present subframe within subframe(s) n−k, with kbelonging to K, where K denotes a set of downlink subframes associatedwith the same uplink subframe in which ACK/NACK feedback is sent. The2-bit DAI may also be included in an uplink grant sent based on DCIformat 0 in LTE. In this case, the DAI may be detected by UE 120 x insubframe n−k′ and may represent the total number of subframes with PDSCHtransmissions and with PDCCH indicating downlink SPS release withinsubframes n−k′, with k′ belonging to K. In each case, the DAI may helpUE 120 x to detect the missing downlink grants, facilitate moreefficient ACK/NACK feedback, and provide other advantages.

In one design, a two-dimensional (2-D) DAI may be used to conveyinformation about scheduled CCs and scheduled subframes formulti-carrier operation in TDD. The 2-D DAI may include two components,DAI_Time and DAI_Freq, to cover time domain and frequency domain,respectively. DAI_Time may be included in a grant when operating in TDD.DAI_Freq may be included in a grant if UE 120 x is configured with twoor more downlink CCs in either FDD or TDD. DAI_Time may comprise twobits and may be provided for each downlink CC. DAI_Time may be includedin a downlink grant or an uplink grant and may indicate the accumulativenumber of PDSCH transmissions (in time) over downlink subframes in adownlink subframe association set on a particular downlink CC. DAI_Freqmay comprise one to three bits and may be provided for each downlinksubframe. DAI_Freq may be included in a downlink grant or an uplinkgrant and may indicate the total number of scheduled CCs and/or whichCCs are scheduled in a given subframe. DAI_Time and/or DAI_Freq may alsoconvey different information dependent on whether they are included in adownlink grant or an uplink grant. For example, DAI_Freq included in adownlink grant may identify the scheduled CCs whereas DAI_Freq includedin an uplink grant may indicate the number of scheduled CCs.

In some situations, it is desirable to reduce the number of ACK/NACKbits for transmission on the uplink. The number of bits of ACK/NACKinformation may be reduced by performing spatial bundling, subframebundling, and/or CC bundling, as described in Table 8.

TABLE 8 Bundling Bundling Type Description Spatial Bundle ACKs and/orNACKs for transport Bundling blocks received via multiple layers on onedownlink CC in one subframe. Subframe Bundle ACKs and/or NACKs fortransport Bundling blocks received on one downlink CC in multiplesubframes. CC Bundle ACKs and/or NACKs for transport Bundling blocksreceived on multiple downlink CCs in one subframe.

In general, a UE may utilize one or more types of bundling to reduce theamount of ACK/NACK feedback. Bundling may be performed in differentmanners depending on various factors such as whether a wireless networkutilizes FDD or TDD, the number of configured CCs, the uplink-downlinkconfiguration in TDD, the desired ACK/NACK payload size, channelconditions, etc.

For spatial bundling, multiple transport blocks may be received viamultiple layers on one downlink CC in one subframe, and an ACK or a NACKmay be obtained for each transport block. A bundled ACK may be generatedif ACKs are obtained for all transport blocks. A bundled NACK may begenerated if a NACK is obtained for any transport block. For subframebundling, multiple transport blocks may be received on one downlink CCin multiple subframes, e.g., one transport block in each subframe. AnACK or a NACK may be obtained for each transport block. A bundled ACKmay be generated if ACKs are obtained for all transport blocks, and abundled NACK may be generated if a NACK is obtained for any transportblock. For CC bundling, multiple transport blocks may be received onmultiple downlink CCs in one subframe, e.g., one transport block oneeach downlink CC. An ACK or a NACK may be obtained for each transportblock. A bundled ACK may be generated if ACKs are obtained for alltransport blocks, and a bundled NACK may be generated if a NACK isobtained for any transport block. With all three types of bundling, wheneNB 110 x receives a bundled NACK, it may retransmit all of theapplicable transport blocks.

In some examples, spatial bundling is utilized with multi-carrieroperation in FDD. Up to M ACK/NACK bits may be generated for Mconfigured CCs, e.g., one ACK/NACK bit for each configured CC orscheduled CC. To improve coverage of ACK/NACK transmission, the numberof configured CCs may be limited and/or ACK/NACK information may be sentwith repetition, e.g., by a factor of 2, 4, or 6. ACK/NACK repetitionmay be utilized when there is little impact to UCI transmission. Forexample, since a CSI transmission may be dropped when an ACK/NACKtransmission is sent, ACK/NACK repetition may be utilized when CSItransmission is not impacted.

In some examples, spatial bundling and subframe bundling may utilizedfor multi-carrier operation in TDD. UE 120 x may be configured with (i)up to five downlink CCs for multi-carrier operation and (ii) anuplink-downlink configuration with up to four downlink subframes to oneuplink subframe for TDD. One or more ACK/NACK feedback modes may besupported, and each ACK/NACK feedback mode may perform bundling in adifferent manner.

In a first ACK/NACK feedback mode for multi-carrier operation in TDD,only one type of bundling may be performed, with the bundling type beingdependent on the number of configured CCs. If one CC is configured, thenonly spatial bundling may be performed to obtain up to four ACK/NACKbits, one ACK/NACK bit for each downlink subframe. If two CCs areconfigured, then only subframe bundling may be performed to obtain up tofour ACK/NACK bits, or up to two ACK/NACK bits for each configured CC orscheduled CC. Alternatively, only spatial bundling may be performed toobtain up to eight ACK/NACK bits, or one ACK/NACK bit for eachconfigured CC in each downlink subframe. If three or more CCs areconfigured, then only subframe bundling may be performed to obtain up to2*M ACK/NACK bits, or up to two ACK/NACK bits for each configured CC orscheduled CC.

In a second ACK/NACK feedback mode for multi-carrier operation in TDD,one or more types of bundling may be performed, with the bundlingtype(s) being dependent on the number of configured CCs. If one CC isconfigured, then only subframe bundling may be performed to obtain up totwo ACK/NACK bits. If two CCs are configured, then both spatial bundlingand subframe bundling may be performed to obtain up to two ACK/NACKbits. If three or more CCs are configured, then both spatial bundlingand subframe bundling may be performed to obtain up to M ACK/NACK bits,e.g., one ACK/NACK bit for each configured CC or scheduled CC.

Bundling may also be performed in other manners. For example, CCbundling may be performed for a subset of the M configured CCs (e.g.,downlink CCs with sufficient correlation) instead of all M configuredCCs. Subframe bundling may be performed for a subset of all downlinksubframes in a radio frame.

The techniques described herein provide various advantages. First, thetechniques may facilitate efficient ACK/NACK feedback for multi-carrieroperation in FDD and TDD. The techniques may also provide multiplexingcapability among different types of UCI, e.g., multiplexing of ACK/NACKand CSI in one subframe. A DAI may cover time domain (for TDD) and/orfrequency domain (for FDD). A DAI may also be defined to be causal, sothat a DAI sent in subframe n does not cover scheduling in subframes n+1and later. This may allow independent scheduling to be maintained acrossdownlink subframes in a bundling window.

FIG. 8 shows an exemplary process 800 for sending ACK/NACK informationin a wireless network. Process 800 may be performed by a UE (asdescribed herein) or by some other entity. The UE may receive a datatransmission on at least one CC in a plurality of CCs configured for theUE (block 812). The UE may determine ACKINACK information for the datatransmission (block 814). The UE may determine an uplink channel forsending the ACK/NACK information (block 816). When the UE sends ACK/NACKinformation on a PUCCH, it may perform power control for sending theACK/NACK information based on the at least one CC on which the datatransmission is received (i.e., at least one detected CC) (block 818).Alternatively, when the UE sends ACK/NACK information on PUSCH, it maydetermine a number of resource elements for sending the ACK/NACKinformation based on the plurality of CCs configured for the UE (block820). The UE may thus considered different CCs (e.g., detected CCs orconfigured CCs) for different purposes and/or to send the ACK/NACKinformation on different uplink channels.

In one example of block 818, the UE may determine the total number oftransport blocks received in the data transmission, e.g., as shown inequation (8). The UE may determine that (i) one transport block isreceived on each CC associated with a downlink grant having a DCI formatsupporting one transport block, and (ii) two transport blocks arereceived on each CC associated with a downlink grant having a DCI formatsupporting two transport blocks. The UE may determine the total numberof transport blocks received in the data transmission based on whetherone or two transport blocks are received on each detected CC. The UE maydetermine a transmit power for sending the ACK/NACK information based onthe total number of transport blocks received by the UE.

In one example of block 820, the UE may determine the total number ofACK/NACK bits for the plurality of CCs. The UE may determine (i) oneACK/NACK bit for each CC configured with a transmission mode supportingone transport block and (ii) two ACK/NACK bits for each CC configuredwith a transmission mode supporting two transport blocks. The UE maydetermine the total number of ACK/NACK bits for the plurality of CCsbased on one or two ACK/NACK bits for each of the plurality of CCs. TheUE may determine the number of resource elements for sending theACK/NACK information based on the total number of ACK/NACK bits for theplurality of CCs.

FIG. 9 shows an exemplary process 900 for receiving ACK/NACK informationin a wireless network. Process 900 may be performed by a basestation/eNB (as described herein) or by some other entity. The basestation may send to a UE a data transmission on at least one CC in aplurality of CCs configured for the UE (block 912). The base station maydetermine an uplink channel for receiving ACK/NACK information for thedata transmission from the UE (block 914). For example, the base stationmay determine that the ACK/NACK information will be received on PUSCHwhen an uplink grant accompanies the data transmission or on PUCCH whenan uplink grant is not provided.

The base station may receive the ACK/NACK information from the UE on aPUCCH at a transmit power determined based on the at least one CC whenit is determined to receive the ACK/NACK information on the PUCCH (block916). In one design, the transmit power may be determined based on thetotal number of transport blocks received by the UE on the at least oneCC. The base station may respond to the detected transmit power bysending power control commands or adjusting data transmission to the UE.When ACK/NACK information is received on the PUSCH, the number ofresource elements utilized may be determined according to the CCs thatare configured for use by the UE. In one example, the number of resourceelements may be determined based on the total number of ACK/NACK bitsfor the plurality of CCs.

FIG. 10 shows an exemplary process 1000 for sending ACK/NACK informationin a wireless network. Process 1000 may be performed by a UE (asdescribed herein) or by some other entity. The UE may receive a datatransmission on at least one CC in a plurality of CCs configured for theUE (block 1012). The UE may determine ACK/NACK information for the datatransmission (block 1014). The UE may determine the total number oftransport blocks received in the data transmission on the at least oneCC (block 1016). The UE may determine a transmit power for sending theACK/NACK information based on the total number of transport blocksreceived by the UE (block 1018). The UE may send the ACK/NACKinformation (e.g., on a PUCCH) based on the determined transmit power(block 1020).

The UE may receive at least one downlink grant intended for the UE. TheUE may identify the at least one CC on which the data transmission isreceived based on the at least one downlink grant.

In one example of block 1016, the UE may determine the number oftransport blocks received on each of the at least one CC. The UE maydetermine the total number of transport blocks received in the datatransmission based on the number of transport blocks received on eachCC. The UE may sum the number of transport blocks received on the atleast one CC in a single subframe. In another example of block 1016, theUE may determine the number of ACK/NACK bits for each of the at leastone CC. The UE may determine the total number of ACK/NACK bits for thedata transmission based on the number of ACK/NACK bits for each CC. Thetotal number of ACK/NACK bits may be equal to the total number oftransport blocks.

As described herein, the UE may determine a PUCCH format for sending theACK/NACK information based on the total number of transport blocksreceived in the data transmission. The UE may send the ACK/NACKinformation based on a PUCCH format supporting two signaling bits andchannel selection. Alternatively, the UE may send the ACK/NACKinformation based on a PUCCH format utilizing DFT-S-OFDM.

Also, the UE may multiplex CSI with the ACK/NACK information in asubframe in which the ACK/NACK information is sent. The UE may determineavailable bits for sending CSI based on the total number of ACK/NACKbits and an available payload size. The UE may multiplex the CSI withthe ACK/NACK information based on the available bits for sending theCSI. In another design, the UE may drop/discard CSI in the subframe inwhich the ACK/NACK information is sent.

FIG. 11 shows an exemplary process 1100 for receiving ACK/NACKinformation in a wireless network. Process 1100 may be performed by abase station/eNB (as described below) or by some other entity. The basestation may send to a UE a data transmission on at least one CC in aplurality of CCs configured for the UE (block 1112). The base stationmay also send at least one downlink grant for the data transmission onthe at least one CC. The base station may receive ACK/NACK informationfor the data transmission from the UE (block 1114). The ACK/NACKinformation may be sent by the UE at a transmit power determined basedon a total number of transport blocks received by the UE in the datatransmission on the at least one CC. The total number of transportblocks may be determined by the UE based on a number of transport blocksreceived by the UE on each of the at least one CC.

FIG. 12 shows an exemplary process 1200 for sending ACK/NACK informationin a wireless network. Process 1200 may be performed by a UE (asdescribed herein) or by some other entity. The UE may receive a datatransmission on at least one CC in a plurality of CCs configured for theUE (block 1212). The UE may determine ACK/NACK information for the datatransmission (block 1214). The UE may determine a number of resourceelements for sending the ACK/NACK information based on the plurality ofCCs configured for the UE (block 1216). The UE may send the ACK/NACKinformation (e.g., on a PUSCH) based on the determined number ofresource elements (block 1218).

In one example of block 1216, the UE may determine the total number ofACK/NACK bits for the plurality of CCs. The UE may determine the numberof resource elements for sending the ACK/NACK information based on thetotal number of ACK/NACK bits for the plurality of CCs.

The UE may order the ACK/NACK bits for the plurality of CCs based on anindex of each CC in the plurality of CCs, e.g., as illustrated by theordered case in FIG. 6. Alternatively, the UE may place the ACK/NACKbit(s) for each CC at a specific position assigned to that CC, e.g., asillustrated by the non-ordered case in FIG. 6.

As described herein, the UE may multiplex CSI with the ACK/NACKinformation in a subframe in which the ACK/NACK information is sent. TheUE may determine available bits for sending the CSI based on the totalnumber of ACK/NACK bits for the plurality of CCs and an availablepayload size. The UE may multiplex the CSI with the ACK/NACK informationbased on the available bits for sending the CSI. In another design, theUE may drop/discard the CSI in the subframe in which the ACK/NACKinformation is sent.

FIG. 13 shows an exemplary process 1300 for receiving ACK/NACKinformation in a wireless network. Process 1300 may be performed by abase station/eNB (as described herein) or by some other entity. The basestation may send to a UE a data transmission on at least one CC in aplurality of CCs configured for the UE (block 1312). The base stationmay determine a number of resource elements for receiving ACK/NACKinformation for the data transmission based on the plurality of CCsconfigured for the UE (block 1314). The number of resource elements maybe determined based on the total number of ACK/NACK bits for theplurality of CCs, and the number of ACK/NACK bits for each CC may bedetermined based on a transmission mode of the CC. The base station mayreceive the ACK/NACK information based on the determined number ofresource elements (block 1316). The ACK/NACK bits for the plurality ofCCs may be ordered based on an index of each CC in the plurality of CCsor may be placed at a specific position for each CC.

The base station may determine available bits for sending CSI based onthe total number of ACK/NACK bits for the plurality of CCs and anavailable payload size. The base station may demultiplex the CSI and theACK/NACK information based on the available bits for sending the CSI.

FIG. 14 shows a block diagram of a design of a base station/eNB 110 yand a UE 120 y, which may be one of the base stations/eNBs and one ofthe UEs in FIG. 1. Within base station 110 y, a module 1410 may generatePDCCH transmissions comprising downlink grants and/or other DCI for oneor more CCs on which UE 120 y is scheduled. A module 1412 may generatePDSCH transmissions comprising data for the scheduled CCs. A transmitter1414 may generate and transmit one or more downlink signals comprisingthe PDCCH and/or PDSCH transmissions. A receiver 1416 may receive andprocess uplink signals transmitted by UE 120 y and other UEs. A module1420 may determine transmission parameters (e.g., an ACK/NACK feedbackscheme, a code rate, etc.) for ACK/NACK information sent by UE 120 y fora data transmission sent by eNB 110 y. A module 1418 may process one ormore received signals in accordance with the ACK/NACK transmissionparameters to recover the ACK/NACK information sent by UE 120 y. Module1418 may also recover CSI and/or other information sent by UE 120 y.

A module 1422 may determine a multi-carrier configuration of UE 120 y,e.g., determine which CCs are configured for UE 120 y for the downlinkand uplink, and which CCs are downlink PCC and uplink PCC for UE 120 y.A module 1424 may determine the ACK/NACK bitwidth and/or the totaltransport block count for UE 120 y based on various factors such aswhether or not DAI is included in grants sent to UE 120 y, theconfigured CCs or scheduled CCs for UE 120 y, whether bundling isperformed, etc. A module 1426 may determine the number of resourceelements used by UE 120 y to send ACK/NACK information on the PUSCH. Thevarious modules within base station 110 y may operate as describedabove. A controller/processor 1428 may direct the operation of variousmodules within base station 110 y. A memory 1430 may store data andprogram codes for base station 110 y. A scheduler 1432 may schedule UEsfor data transmission.

Within UE 120 y, a receiver 1450 may receive and process downlinksignals from base station 110 y and other base stations. A module 1452may process (e.g., demodulate and decode) one or more received signalsto recover PDCCH transmissions sent to UE 120 y. A module 1454 mayprocess the received signal(s) to recover PDSCH transmissions sent to UE120 y. A module 1458 may determine ACK/NACK information for the receiveddata transmission. A module 1456 may determine transmission parametersfor sending the ACK/NACK information. Module 1458 may send the ACK/NACKinformation on the PUCCH or PUSCH in accordance with the ACK/NACKtransmission parameters. Module 1458 may also send CSI and/or otherinformation on the PUCCH or PUSCH. A transmitter 1460 may generate andtransmit one or more uplink signals comprising a PUCCH transmission or aPUSCH transmission.

A module 1468 may determine a multi-carrier configuration of UE 120 y,e.g., determine which CCs are configured for UE 120 y for the downlinkand uplink, and which CCs are downlink PCC and uplink PCC for UE 120 y.A module 1462 may determine the ACK/NACK bitwidth and/or the totaltransport block count for UE 120 y based on various factors such aswhether or not DAI is included in grants sent to UE 120 y, theconfigured CCs or scheduled CCs for UE 120 y, whether bundling isperformed, etc. A module 1464 may perform power control for the PUCCHbased on the ACK/NACK bitwidth and/or the total transport block count,e.g., determine the transmit power for sending the ACK/NACK informationon the PUCCH. A module 1466 may determine the number of resourceelements for sending the ACK/NACK information on the PUSCH. The variousmodules within UE 120 y may operate as described above. Acontroller/processor 1470 may direct the operation of various moduleswithin UE 120 y. A memory 1472 may store data and program codes for UE120 y.

The modules in FIG. 14 may comprise processors, electronic devices,hardware devices, electronic components, logical circuits, memories,software codes, firmware codes, etc., or any combination thereof.

FIG. 15 shows a block diagram of a design of a base station/eNB 110 zand a UE 120 z, which may be one of the base stations/eNBs and one ofthe UEs in FIG. 1. Base station 110 z may be equipped with T antennas1534 a through 1534 t, and UE 120 z may be equipped with R antennas 1552a through 1552 r, where in general T≧1 and R≧1.

At base station 110 z, a transmit processor 1520 may receive data from adata source 1512 for transmission on one or more downlink CCs to one ormore UEs, process (e.g., encode and modulate) the data for each UE basedon one or more modulation and coding schemes selected for that UE, andprovide data symbols for all UEs. Transmit processor 1520 may alsoprocess control information (e.g., for grants, DAI, configurationmessages, etc.) and provide control symbols. Processor 1520 may alsogenerate reference symbols for reference signals. A transmit (TX) MIMOprocessor 1530 may precode the data symbols, the control symbols, and/orthe reference symbols (if applicable) and may provide T output symbolstreams to T modulators (MOD) 1532 a through 1532 t. Each modulator 1532may process its output symbol stream (e.g., for OFDM, etc.) to obtain anoutput sample stream. Each modulator 1532 may further condition (e.g.,convert to analog, amplify, filter, and upconvert) its output samplestream to obtain a downlink signal. T downlink signals from modulators1532 a through 1532 t may be transmitted via T antennas 1534 a through1534 t, respectively.

At UE 120 z, antennas 1552 a through 1552 r may receive the downlinksignals from base station 110 z and/or other base stations and mayprovide received signals to demodulators (DEMODs) 1554 a through 1554 r,respectively. Each demodulator 1554 may condition (e.g., filter,amplify, downconvert, and digitize) its received signal to obtain inputsamples. Each demodulator 1554 may further process the input samples(e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 1556may obtain received symbols from all R demodulators 1554 a through 1554r, perform MIMO detection on the received symbols, and provide detectedsymbols. A receive processor 1558 may process (e.g., demodulate anddecode) the detected symbols, provide decoded data for UE 120 z to adata sink 1560, and provide decoded control information to acontroller/processor 1580.

On the uplink, at UE 120 z, a transmit processor 1564 may receive andprocess data from a data source 1562 and control information (e.g.,ACKNACK information, CSI, etc.) from controller/processor 1580.Processor 1564 may also generate reference symbols for one or morereference signals. The symbols from transmit processor 1564 may beprecoded by a TX MIMO processor 1566 if applicable, further processed bymodulators 1554 a through 1554 r (e.g., for SC-FDM, OFDM, etc.), andtransmitted to base station 110 z. At base station 110 z, the uplinksignals from UE 120 z and other UEs may be received by antennas 1534,processed by demodulators 1532, detected by a MIMO detector 1536 ifapplicable, and further processed by a receive processor 1538 to obtaindecoded data and control information sent by UE 120 z and other UEs.Processor 1538 may provide the decoded data to a data sink 1539 and thedecoded control information to controller/processor 1540.

Controllers/processors 1540 and 1580 may direct the operation at basestation 110 z and UE 120 z, respectively. Processor 1540 and/or otherprocessors and modules at base station 110 z may perform or directprocess 900 in FIG. 9, process 1100 in FIG. 11, process 1300 in FIG. 13,and/or other processes for the techniques described herein. Processor1580 and/or other processors and modules at UE 120 z may perform ordirect process 800 in FIG. 8, process 1000 in FIG. 10, process 1200 inFIG. 12, and/or other processes for the techniques described herein.Memories 1542 and 1582 may store data and program codes for base station110 z and UE 120 z, respectively. A scheduler 1544 may schedule UEs fordata transmission on the downlink and/or uplink.

It will be recognized that information and signals may be representedusing any of a variety of different technologies and techniques. Forexample, data, instructions, commands, information, signals, bits,symbols, and chips that may be referenced throughout the abovedescription may be represented by voltages, currents, electromagneticwaves, magnetic fields or particles, optical fields or particles, or anycombination thereof.

Also, it will be appreciated that the various illustrative logicalblocks, modules, circuits, and algorithm steps described in connectionwith the disclosure herein may be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), then the coaxial cable,fiber optic cable, twisted pair, or DSL are included in the definitionof medium. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andblu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communication, comprising:receiving a data transmission on at least one component carrier (CC) ina plurality of CCs configured for a user equipment (UE); determiningacknowledgement/negative acknowledgement (ACK/NACK) information for thedata transmission; determining a number of resource elements for sendingthe ACK/NACK information based on the plurality of CCs configured forthe UE; and sending the ACK/NACK information based on the determinednumber of resource elements.
 2. The method of claim 1, wherein thedetermining the number of resource elements comprises: determining atotal number of ACK/NACK bits for the plurality of CCs, and determiningthe number of resource elements for sending the ACK/NACK informationbased on the total number of ACK/NACK bits.
 3. The method of claim 2,wherein the determining the total number of ACK/NACK bits comprises:determining one ACK/NACK bit for each CC configured with a transmissionmode supporting one transport block, determining two ACK/NACK bits foreach CC configured with a transmission mode supporting two transportblocks, and determining the total number of ACK/NACK bits for theplurality of CCs based on one or two ACK/NACK bits for each of theplurality of CCs.
 4. The method of claim 2, further comprising: orderingACK/NACK bits for the plurality of CCs based on an index of each CC inthe plurality of CCs.
 5. The method of claim 1, wherein the sending theACK/NACK information comprises: sending the ACK/NACK information on aphysical uplink shared channel (PUSCH) based on the determined number ofresource elements.
 6. The method of claim 5, further comprising:multiplexing channel state information (CSI) with the ACK/NACKinformation on the PUSCH.
 7. An apparatus for wireless communication,comprising: means for receiving a data transmission on at least onecomponent carrier (CC) in a plurality of CCs configured for a userequipment (UE); means for determining acknowledgement/negativeacknowledgement (ACK/NACK) information for the data transmission; meansfor determining a number of resource elements for sending the ACK/NACKinformation based on the plurality of CCs configured for the UE; andmeans for sending the ACK/NACK information based on the determinednumber of resource elements.
 8. The apparatus of claim 7, wherein themeans for determining the number of resource elements comprises: meansfor determining a total number of ACK/NACK bits for the plurality ofCCs, and means for determining the number of resource elements forsending the ACK/NACK information based on the total number of ACK/NACKbits for the plurality of CCs.
 9. The apparatus of claim 8, wherein themeans for determining the total number of ACK/NACK bits comprises: meansfor determining one ACK/NACK bit for each CC configured with atransmission mode supporting one transport block, means for determiningtwo ACK/NACK bits for each CC configured with a transmission modesupporting two transport blocks, and means for determining the totalnumber of ACK/NACK bits for the plurality of CCs based on one or twoACK/NACK bits for each of the plurality of CCs.
 10. The apparatus ofclaim 8, further comprising: means for ordering ACK/NACK bits for theplurality of CCs based on an index of each CC in the plurality of CCs.11. The apparatus of claim 7, wherein the means for sending the ACK/NACKinformation comprises: means for sending the ACK/NACK information on aphysical uplink shared channel (PUSCH) based on the determined number ofresource elements.
 12. The apparatus of claim 11, further comprising:means for multiplexing channel state information (CSI) with the ACK/NACKinformation on the PUSCH.
 13. An apparatus for wireless communication,comprising: at least one processor configured to: receive a datatransmission on at least one component carrier (CC) in a plurality ofCCs configured for a user equipment (UE), determineacknowledgement/negative acknowledgement (ACK/NACK) information for thedata transmission, determine a number of resource elements for sendingthe ACK/NACK information based on the plurality of CCs configured forthe UE, and send the ACK/NACK information based on the determined numberof resource elements; and a memory coupled to the at least oneprocessor.
 14. The apparatus of claim 13, wherein the at least oneprocessor is configured to: determine a total number of ACK/NACK bitsfor the plurality of CCs, and determine the number of resource elementsfor sending the ACK/NACK information based on the total number ofACK/NACK bits for the plurality of CCs.
 15. The apparatus of claim 14,wherein the at least one processor is configured to determine the totalnumber of ACK/NACK bits at least in part by: determining one ACK/NACKbit for each CC configured with a transmission mode supporting onetransport block, determining two ACK/NACK bits for each CC configuredwith a transmission mode supporting two transport blocks, anddetermining the total number of ACK/NACK bits for the plurality of CCsbased on one or two ACK/NACK bits for each of the plurality of CCs. 16.The apparatus of claim 15 wherein the at least one processor is furtherconfigured to: order ACK/NACK bits for the plurality of CCs based on anindex of each CC in the plurality of CCs.
 17. The apparatus of claim 13,wherein the at least one processor is configured to send the ACK/NACKinformation on a physical uplink shared channel (PUSCH) based on thedetermined number of resource elements.
 18. The apparatus of claim 17,further comprising: multiplexing channel state information (CSI) withthe ACK/NACK information on the PUSCH.
 19. A non-transitorycomputer-readable medium having program code recorded thereon, theprogram code comprising: code for causing at least one processor toreceive a data transmission on at least one component carrier (CC) in aplurality of CCs configured for a user equipment (UE), code for causingthe at least one processor to determine acknowledgement/negativeacknowledgement (ACK/NACK) information for the data transmission, codefor causing the at least one processor to determine a number of resourceelements for sending the ACK/NACK information based on the plurality ofCCs configured for the UE, and code for causing the at least oneprocessor to send the ACK/NACK information based on the determinednumber of resource elements.
 20. The non-transitory computer-readablemedium of claim 19, wherein the code for causing the at least oneprocessor to determine the number of resource elements comprises: codefor causing the at least one processor to determine a total number ofACK/NACK bits for the plurality of CCs, and code for causing the atleast one processor to determine the number of resource elements forsending the ACK/NACK information based on the total number of ACK/NACKbits for the plurality of CCs.
 21. The non-transitory computer-readablemedium of claim 20, wherein the code for causing the at least oneprocessor to determine the total number of ACK/NACK bits comprises: codefor causing the at least one processor to determine one ACK/NACK bit foreach CC configured with a transmission mode supporting one transportblock, code for causing the at least one processor to determine twoACK/NACK bits for each CC configured with a transmission mode supportingtwo transport blocks, and code for causing the at least one processor todetermine the total number of ACK/NACK bits for the plurality of CCsbased on one or two ACK/NACK bits for each of the plurality of CCs. 22.The non-transitory computer-readable medium of claim 20, furthercomprising: code for causing the at least one processor to orderACK/NACK bits for the plurality of CCs based on an index of each CC inthe plurality of CCs.
 23. The non-transitory computer-readable medium ofclaim 19, wherein the code for causing the at least one processor tosend the ACK/NACK information comprises: code for causing the at leastone processor to send the ACK/NACK information on a physical uplinkshared channel (PUSCH) based on the determined number of resourceelements.
 24. The non-transitory computer-readable medium of claim 23,further comprising: code for causing the at least one processor tomultiplex channel state information (CSI) with the ACK/NACK informationon the PUSCH.
 25. A method for wireless communication, comprising:sending, to a user equipment (UE), a data transmission on at least onecomponent carrier (CC) in a plurality of CCs configured for the UE;determining a number of resource elements for receivingacknowledgement/negative acknowledgement (ACK/NACK) information for thedata transmission based on the plurality of CCs configured for the UE;and receiving the ACK/NACK information based on the determined number ofresource elements.
 26. The method of claim 25, wherein the number ofresource elements is determined based on a total number of ACK/NACK bitsfor the plurality of CCs configured for the UE, and wherein a number ofACK/NACK bits for each of the plurality of CCs is determined based on atransmission mode of the CC.
 27. The method of claim 25, whereinACK/NACK bits for the plurality of CCs are ordered based on an index ofeach CC in the plurality of CCs.
 28. An apparatus for wirelesscommunication, comprising: means for sending, to a user equipment (UE),a data transmission on at least one component carrier (CC) in aplurality of CCs configured for the UE; means for determining a numberof resource elements for receiving acknowledgement/negativeacknowledgement (ACK/NACK) information for the data transmission basedon the plurality of CCs configured for the UE; and means for receivingthe ACK/NACK information based on the determined number of resourceelements.
 29. The apparatus of claim 28, wherein the number of resourceelements is determined based on a total number of ACK/NACK bits for theplurality of CCs configured for the UE, and wherein a number of ACK/NACKbits for each of the plurality of CCs is determined based on atransmission mode of the CC.
 30. The apparatus of claim 28, whereinACK/NACK bits for the plurality of CCs are ordered based on an index ofeach CC in the plurality of CCs.
 31. An apparatus for wirelesscommunication, comprising: at least one processor configured to: send,to a user equipment (UE), a data transmission on at least one componentcarrier (CC) in a plurality of CCs configured for the UE, determine anumber of resource elements for receiving acknowledgement/negativeacknowledgement (ACK/NACK) information for the data transmission basedon the plurality of CCs configured for the UE, and receive the ACK/NACKinformation based on the determined number of resource elements; and amemory coupled to the at least one processor.
 32. The apparatus of claim31, wherein the number of resource elements is determined based on atotal number of ACK/NACK bits for the plurality of CCs configured forthe UE, and wherein a number of ACK/NACK bits for each of the pluralityof CCs is determined based on a transmission mode of the CC.
 33. Theapparatus of claim 31, wherein ACK/NACK bits for the plurality of CCsare ordered based on an index of each CC in the plurality of CCs.
 34. Anon-transitory computer-readable medium comprising: code for causing atleast one processor to send, to a user equipment (UE), a datatransmission on at least one component carrier (CC) in a plurality ofCCs configured for the UE, code for causing the at least one processorto determine a number of resource elements for receivingacknowledgement/negative acknowledgement (ACK/NACK) information for thedata transmission based on the plurality of CCs configured for the UE,and code for causing the at least one processor to receive the ACK/NACKinformation based on the determined number of resource elements.
 35. Thenon-transitory computer-readable medium of claim 34, wherein the numberof resource elements is determined based on a total number of ACK/NACKbits for the plurality of CCs configured for the UE, and wherein anumber of ACK/NACK bits for each of the plurality of CCs is determinedbased on a transmission mode of the CC.
 36. The non-transitorycomputer-readable medium of claim 35, wherein ACK/NACK bits for theplurality of CCs are ordered based on an index of each CC in theplurality of CCs.